Overview of Managing Access Permissions to Your
AWS Storage Gateway

Every AWS resource is owned by an AWS account, and permissions to create or access
a
resource are governed by permissions policies. An account administrator can attach
permissions
policies to IAM identities (that is, users, groups, and roles), and some services
(such as AWS
Lambda) also support attaching permissions policies to resources.

Note

An account administrator (or administrator user) is a user with
administrator privileges. For more information, see IAM Best Practices in the IAM User
Guide.

When granting permissions, you decide who is getting the permissions, the resources
they
get permissions for, and the specific actions that you want to allow on those
resources.

AWS Storage Gateway Resources and Operations

In AWS Storage Gateway, the primary resource is a gateway. Storage Gateway also
supports the following additional resource types: file share, volume,
virtual tape, iSCSI target, and vtl
device. These are referred to as subresources and they
don't exist unless they are associated with a gateway.

These resources and subresources have unique Amazon Resource Names (ARNs) associated
with them as shown in the following table.

AWS Storage Gateway resource IDs are in uppercase. When you use these resource IDs
with the
Amazon EC2 API, Amazon EC2 expects resource IDs in lowercase. You must change your
resource ID
to lowercase to use it with the EC2 API. For example, in Storage Gateway the ID for
a
volume might be vol-1122AABB. When you use this ID with the EC2 API, you
must change it to vol-1122aabb. Otherwise, the EC2 API might not behave
as expected.

ARNs for gateways activated prior to September 2, 2015, contain the gateway name
instead of the gateway ID. To obtain the ARN for your gateway, use the
DescribeGatewayInformation API operation.

To grant permissions for specific API operations, such as creating a tape, AWS Storage
Gateway
provides a set of API actions for you to create and manage these resources and subresources.
For a list of API actions, see Actions in the AWS Storage Gateway API Reference.

To grant permissions for specific API operations, such as creating a tape, AWS Storage
Gateway
defines a set of actions that you can specify in a permissions policy to grant permissions
for specific API operations. An API operation can require permissions for more than
one
action. For a table showing all the AWS Storage Gateway API actions and the resources
they apply to, see
AWS Storage Gateway API Permissions: Actions, Resources, and
Conditions Reference.

Understanding Resource Ownership

A resource owner is the AWS account that created the resource. That
is, the resource owner is the AWS account of the principal entity (the
root account, an IAM user, or an IAM role) that authenticates the request that creates
the
resource. The following examples illustrate how this works:

If you use the root account credentials of your AWS account to activate a gateway,
your AWS account is the owner of the resource (in AWS Storage Gateway, the resource
is the
gateway).

If you create an IAM user in your AWS account and grant permissions to the
ActivateGateway action to that user, the user can activate a gateway.
However, your AWS account, to which the user belongs, owns the gateway
resource.

If you create an IAM role in your AWS account with permissions to activate a
gateway, anyone who can assume the role can activate a gateway. Your AWS account,
to
which the role belongs, owns the gateway resource.

Managing Access to Resources

A permissions policy describes who has access to what. The following section explains
the available options for creating permissions policies.

Note

This section discusses using IAM in the context of AWS Storage Gateway. It doesn't
provide
detailed information about the IAM service. For complete IAM documentation, see What is IAM in the IAM User Guide. For
information about IAM policy syntax and descriptions, see AWS IAM Policy Reference in the IAM User
Guide.

Policies attached to an IAM identity are referred to as
identity-based policies (IAM polices) and policies attached to a
resource are referred to as resource-based policies. AWS Storage Gateway supports
only identity-based policies (IAM policies).

Identity-Based Policies (IAM Policies)

You can attach policies to IAM identities. For example, you can do the
following:

Attach a permissions policy to a user or a group in your
account – An account administrator can use a permissions policy
that is associated with a particular user to grant permissions for that user to create
an AWS Storage Gateway resource, such as a gateway, volume, or tape.

Attach a permissions policy to a role (grant cross-account
permissions) – You can attach an identity-based permissions policy
to an IAM role to grant cross-account permissions. For example, the administrator
in
Account A can create a role to grant cross-account permissions to another AWS account
(for example, Account B) or an AWS service as follows:

Account A administrator creates an IAM role and attaches a permissions
policy to the role that grants permissions on resources in Account A.

Account A administrator attaches a trust policy to the role identifying
Account B as the principal who can assume the role.

Account B administrator can then delegate permissions to assume the role to
any users in Account B. Doing this allows users in Account B to create or access
resources in Account A. The principal in the trust policy can also be an AWS
service principal if you want to grant an AWS service permissions to assume the
role.

For more information about using IAM to delegate permissions, see Access Management in the
IAM User Guide.

The following is an example policy that grants permissions to all List*
actions on all resources. This action is a read-only action. Thus, the policy doesn't
allow the user to change the state of the resources.

Resource-Based Policies

Other services, such as Amazon S3, also support resource-based permissions policies.
For
example, you can attach a policy to an S3 bucket to manage access permissions to that
bucket. AWS Storage Gateway doesn't support resource-based policies.

For each AWS Storage Gateway resource (see AWS Storage Gateway API Permissions: Actions, Resources, and
Conditions Reference), the service defines a set of API operations
(see Actions). To grant permissions
for these API operations, AWS Storage Gateway defines a set of actions that you can
specify in a policy.
For example, for the AWS Storage Gateway gateway resource, the following actions are
defined:
ActivateGateway, DeleteGateway, and
DescribeGatewayInformation. Note that, performing an API operation can
require permissions for more than one action.

The following are the most basic policy elements:

Resource – In a policy, you use an Amazon
Resource Name (ARN) to identify the resource to which the policy applies. For AWS
Storage Gateway
resources, you always use the wildcard character (*) in IAM policies. For
more information, see AWS Storage Gateway Resources and Operations.

Action – You use action keywords to identify
resource operations that you want to allow or deny. For example, depending on the
specified Effect, the storagegateway:ActivateGateway
permission allows or denies the user permissions to perform the AWS Storage Gateway
ActivateGateway operation.

Effect – You specify the effect when the
user requests the specific action—this can be either allow or deny. If you don't
explicitly grant access to (allow) a resource, access is implicitly denied. You can
also
explicitly deny access to a resource, which you might do to make sure that a user
cannot
access it, even if a different policy grants access.

Principal – In identity-based policies
(IAM policies), the user that the policy is attached to is the implicit principal.
For
resource-based policies, you specify the user, account, service, or other entity that
you want to receive permissions (applies to resource-based policies only). AWS Storage
Gateway
doesn't support resource-based policies.

Specifying Conditions in a Policy

When you grant permissions, you can use the IAM policy language to specify the
conditions when a policy should take effect when granting permissions. For example,
you
might want a policy to be applied only after a specific date. For more information
about
specifying conditions in a policy language, see Condition in the
IAM User Guide.

To express conditions, you use predefined condition keys. There are no condition keys
specific to Storage Gateway. However, there are AWS-wide condition keys that you can
use as
appropriate. For a complete list of AWS-wide keys, see Available Keys
in the IAM User Guide.